U.S. Pat. No. 4,559,314, the contents of which are incorporated herein by reference, discloses a method for activating zeolites by compositing with an alumina binder containing water and thereafter contacting with steam.
U.S. Pat. No. 4,780,444, the contents of which are incorporated herein by reference, discloses a method for activating metallophosphates such as aluminophosphates (AlPOs) with an activating metal oxide, such as silica, and water under conditions, such as mulling, sufficient to increase the acid catalytic activity of the material.
Crystalline, microporous silicoaluminophosphates (SAPOs) are described in the Lok et al U.S. Pat. No. 4,440,871, the entire disclosure of which is expressly incorporated herein by reference. Partial substitution of aluminum for phosphorus in silicoaluminophosphate frameworks in order to generate catalytically active acid sites has been a long-standing goal of this area of molecular sieve science. For the most part, significant catalytic activity has not been achieved. This may result from the bulk silicon content being present as coprecipitated silica, or, as silicon-rich islands within the framework affording few active Si-O-Al interactions. The present invention provides a method for enhancing acid activity by increasing the number of acid sites, i.e., tetrahedral aluminum in the SAPO framework.